Arithmetic
by Empatheia
Summary: [Kaoru x Haruhi x Hikaru] Fractions and partials, two or three or only one? For Kaoru, love must make sense.


**A/N: **Written for **kikoeru ka **for the June round of flashfics on LiveJournal. Enjoy:D

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_**Arithmetic**_

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_**a·rith·me·tic**_

_n._

_1. The mathematics of integers, rational numbers, real numbers, or complex numbers under addition, subtraction, multiplication, and division._

_2. Archaic: A book on this kind of mathematics._

By the end of senior year, the number of people Hitachiin Kaoru cared about enough to save from drowning was this: precisely two, no more and

This was an improvement, as the year before the same count would have resulted in a number only half of that, which was a little on the depressing side in everyone's view but his. In his eyes, two people was more than enough, maybe even too much. His was a heart born to love with singular focus.

For the first decade of his life and most of the second, there had been no problem with this. Hikaru was his life... the other half of his pale and windblown soul, the rakishly grinning life-sized mirror that followed him everywhere he went. (Most people thought it was he who followed Hikaru, but this was not so. The number of people who understood that truth aside from himself was also two.)

Kaoru had eyes that could see around the corners of hearts, and he was often cruel with what he found there. It was not because he was a bad person. It was because he understood people better when they were angry and hurt than he did when they were happy, and he felt more comfortable being in their presence when he could understand them. It was simple self-preservation, not malice as many thought.

Once again, the number of people who understood that about him was two-- no more, and no less.

The first person was, naturally, Hikaru. The two of them could not misunderstand each other even if they tried, and so they had given up years and years ago.

The name of the second person was Fujioka Haruhi, and Kaoru still could not get used to the taste of it in his mouth.

He had always thought that having someone be able to tell them apart would be wonderful, a dream worth remembering and wishing for. When the reality came, it was both better and far worse than he had imagined. Being recognized as a person individual and separate from Hikaru was a beautiful, wondrous thing he had still not managed to get over.

However, it was also terrifying in a unique way that was difficult to describe.

It was like this-- being recognized as his own person signified to him a sort of aloneness that he had never felt before. If he was one person, and not two, then there was no one to hide beside and within. He was a singular pronoun, a prime number divisible by nothing but himself, a being with borders that did not include any other being.

He could not say out loud how badly this frightened him, but it did.

And once again, Haruhi understood.

This frightened him even more. He was familiar with being a twin, comfortable with being one of two, or half of one.

Being a third, one of three, was new and strange.

It was a constant wonder to him that though it was frightening, he had also-- at the same time-- probably never been happier in his life.

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Hikaru was the one who _did_ things. Kaoru was the one who stood in the shadows and observed, understanding more but feeling less.

He wasn't sure he would ever understand what Hikaru felt in moments like this one, when he held Haruhi in his arms and pressed his lips to hers and closed his eyes and forgot about thinking for quiet, glorious minutes at a time. He wasn't sure it would ever make sense to him when Haruhi's eyes closed as well and her arms crept around Hikaru's neck, meeting him halfway in their sojourn of unreasoning bliss.

Somehow, though, he wanted to understand.

So, after school one day, he caught her by the arm and pulled her into a shadowed alcove. He hadn't planned what to say in advance, or even solidified his reasons for doing this, but his mind told him that this was a necessary step to getting it (whatever 'it' was), and so he was-- for once-- just going with the flow of things.

She asked him what the matter was, and he told her that the matter was too complicated to talk about. It was true, but he felt like a coward for saying it anyway. It felt like a cop-out.

To mask his irritating feelings, he scrutinized her eyes carefully for a moment, then kissed her. It was almost clinical, detached and formulaic.

Haruhi, predictably, hit him, and not lightly either. She did not think of herself as a girl, he knew, and so her blows did not land delicately as a woman's should. Blood rushed to his cheek and he knew it would leave a mark the next day.

"If you're going to do something like that, you had better mean it," she said coldly, then turned and strode off without looking back.

Kaoru filed away the information for future scrutiny, and nursed his swelling cheek.

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Hikaru was torn.

It was so obvious, but he refused to say a word about it. Haruhi, or his brother? He seemed to believe that the two were mutually exclusive, and Kaoru couldn't honestly say yet that they weren't.

Kaoru still didn't understand Haruhi. He spent hours watching, listening, and thinking, but it still did not make sense to him how she could simply take each of them as they were, without trying to change them in the slightest. It was human nature to do that, and so by that measure, Haruhi was inhuman.

And yet, that was resoundingly inaccurate, and Kaoru could not put his finger on exactly why.

She was a mystery, and yet she made no attempt to hide anything.

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Next time, instead of him pulling her aside, _she_ pulled _him_ aside into the shadow of a pillar and met his eyes earnestly.

"Like _this_," she told him, and then kissed him like he had seen her kiss Hikaru-- hands tangled in his hair, eyes closed and body uncharacteristically yielding.

The difference was palpable. There was humanity in this, truth in this, _reality_ in this. It was not an experiment. It was a _statement._

"Oh," he said when she released him. Then he curved his palms around her face and regarded her thoughtfullyl for a moment. "I see." Then he kissed her... properly this time, with one hand around the nape of her neck and the other curling into the hair framing her face.

When he let her go, the first thing she did was smile. "Much better," she said. Then she walked away again, just like last time except that this time, she was smiling.

Kaoru thought that maybe he understood a little bit now, at least somewhat more than he had understood before.

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He found them again in the same place, hiding from the world but not from him, tangled and wrapped up in each other.

Kaoru knew how much effort and agony Hikaru had put into making Haruhi reciprocate his feelings. He did not begrudge them this quiet warm-dark moment away from the eyes of the world, but neither was he satisfied with seeing and doing nothing.

So, disregarding their vulnerable state, he walked into the shadow to join them and buried his face in Haruhi's hair without saying a word or asking permission. In return, without saying a word of her own, she reached around and caught his left hand in her own, drawing him into the silent bubble that had only contained her and Hikaru a moment before.

He still didn't understand. But somehow, now, he understood at least that he _wanted_ to understand.

Haruhi, as always, understood.

Hikaru understood whether he wanted to or not.

Kaoru let himself forget logic for a moment, just long enough to enjoy being a third of a whole, then pulled away. Step by cautious step was the way to go, he'd learned over years of difficulty and painful change, and so he would not allow more than this one moment for now.

There were infinite moments waiting in the future, and those he would not waste.

Haruhi (as though she could hear his thoughts) smiled, and refused to let go of his hand.

After a while, he stopped trying to free himself. It was then that he, to his utter astonishment, discovered that he had actually been free all along, and simply had not known how to recognize it. Now he did, and it was so much simpler than he'd expected it to be.

Her hand was warmer than his.

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**A/N:** I hope you enjoyed it! ♥


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